Thermally actuated cantilevered beam optical scanner

ABSTRACT

Embodiments of optical scanners, optical projection systems, and methods of scanning optical waveguides and projecting images are described. The disclosed devices, systems and methods advantageously provide an improvement to the compactness, robustness, simplicity, and reliability of optical scanners and optical projection systems by implementing a thermally driven actuator for inducing oscillations of a cantilever within the optical scanners and optical projection systems. The stability and accuracy of optical scanners and optical projection systems are further enhanced using capacitive sensing, feedback, and phase correction techniques described herein.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/197,165, filed on Nov. 20, 2018, entitled “THERMALLY ACTUATEDCANTILEVERED BEAM OPTICAL SCANNER,” which is a non-provisional of andclaims the benefit of and priority to U.S. Provisional PatentApplication No. 62/590,073, filed Nov. 22, 2017, entitled “THERMALLYACTUATED CANTILEVERED BEAM OPTICAL SCANNER,” the contents of which arehereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

Since the advent of the smartphone, the great utility of having aversatile and always available device capable of general purposecomputing and multimedia communication has been realized by the publicat large. Nonetheless a pronounced drawback of smartphones is therelatively small screen size. Smartphone display screens are a smallfraction of the size of even small laptop computer screens.

It is now contemplated that smartphones will eventually be replaced orindispensably supplemented by augmented reality glasses that will, amongother things, effectively provide users with a relatively large field ofview 3D imagery output system that is accessible to users, at will,whether for business or entertainment purposes.

SUMMARY OF THE INVENTION

Beyond merely exceeding the screen size afforded by a laptop and withoutthe encumbrance of carrying a laptop, augmented reality glasses willprovide new mixed reality applications that seamlessly integrate thereal world and virtual content. This not only preserves the user'sengagement with the real world, but also enables new types ofaugmentation of the physical world, such as, for example: automaticallygenerated contextually relevant information overlaid on automaticallyrecognized real world objects; communication between remotely situatedpersons through 3D dimensional avatars of each party presented at theother party's location; and mixed reality games that include virtualcontent behaving realistically, e.g., respecting boundaries of physicalobjects in the real world.

One form of augmented reality includes a set of transparent eyepiecesthat are configured to couple light from left and right sources ofimagewise modulated light to a user's eyes. Thus the user can view thereal world while simultaneously viewing virtual imagery. Separate leftand right imagery that is stereoscopically correct may be provided.Additionally the curvature of the wavefront of light carrying theimagery can be controlled based on the intended distance of virtualobjects included in the virtual imagery from the user. Both of theforegoing measures contribute to the user's perception that viewedimagery is three dimensional. A substantially diminished form ofaugmented reality glasses can provide a small field of view of virtualimagery to one eye.

It would be desirable to reduce the size and weight of augmented realityglasses to values approaching those of typical eyeglasses. An obstacleto doing so is often the source of imagewise modulated light. Evenhighly miniaturized projectors based on 2D focal plane array lightmodulators as Liquid Crystal on Silicon (LCoS), or Digital MicromirrorDevice (DMD) will typically occupy a few cubic centimeters of volume andweight a few grams. One highly compact source of imagewise modulatedlight is the fiber scanner. The fiber scanner includes an optical fiberextending through a piezoelectric drive tube. Construction of the fiberscanner involves painstaking manual assembly and epoxy bondingprocedures which would be a cost issue for a mass produced product.Another issue with fiber scanners can be the significant unit-to-unitvariations in the piezoelectric drive tubes. A further issue with fiberscanners is that the imagery they produce is somewhat distorted and thedistortion varies from one video frame to the next. The distortion isbelieved to be attributable in part to the variations in thepiezoelectric scanner tubes and possibly variations resulting from theassembly of the fiber and the piezoelectric scanner tube.

Therefore, there is a need in the art for a compact optical scannersuitable for compact augmented reality glasses that is amenable to massproduction and includes provisions for scan pattern control.

This application relates to optical scanning and projection systems andmethods of projecting images. More specifically, and without limitation,this application relates to thermally driven microcantilever-basedoptical scanners and projection systems and associated methods ofprojecting images. The disclosed microcantilever-based optical scannersand projection systems include cantilevered beams having a set ofresistive heating elements for inducing controllable thermal expansionin the cantilevered beams in order to oscillate the cantilevered beamsin a desirable fashion to allow projection of a two-dimensional image.

In an aspect, optical scanning devices are described. For example, anoptical scanning device may comprise a base, a cantilevered beamextending from the base, such as a cantilevered beam that includes aproximal end attached to the base and a distal end (e.g., a free orunsupported distal end), at least one optical waveguide positioned onthe base and the cantilevered beam and extending from the base along thecantilevered beam from the proximate end to the distal end, and aplurality of heaters disposed on the cantilevered beam.

A variety of heater configurations are useful with the optical scanningdevices described herein. For example, optionally, the plurality ofheaters are disposed on the cantilevered beam proximate to the proximalend. In a specific embodiment, the plurality of heaters comprise fourheaters. Optionally, the plurality of heaters are spaced about thecantilevered beam. For example, the cantilevered beam may have a topside and a bottom side, and, optionally, the plurality of heatersincludes a first heater, a second heater, a third heater, and a fourthheater. In one arrangement, a first heater and a second heater aredisposed on the top side and a third heater and a fourth heater aredisposed on the bottom side. Optionally, the heaters are disposed oncorners of the cantilevered beam, such as where the cantilevered beamhas a rectangular cross section.

The cantilevered beam, the base, and/or other components may befabricated using techniques of microfabrication, including patterning,masking, lithography, etching, deposition, lift-off, sacrificial layersor substrates, etc. Various materials and constructions may be used.

For example, the cantilevered beam and the base may optionally bemonolithic and integrally formed, such as from a single crystal orpolycrystalline material. Optionally, the cantilevered beam and/or thebase may comprise silicon carbide, silicon, or diamond. These materialsmay be useful, in embodiments, as these materials exhibit large heatconductivities, which may be considerably greater than other materials,such as silicon dioxide or silicon nitride. Optionally, the heaters maycomprise resistive materials, such as platinum or silicon, e.g., dopedsilicon. Optionally, the heaters are patterned in specific locations onthe cantilevered beam to provide precise locations for introduction ofheat to induce thermal expansion in the cantilevered beam to causeoscillations to occur by repeated and alternating heating of thecantilevered beam followed by thermal relaxation by conduction of theheat from the cantilevered beam to the base. In embodiments, the opticalscanning device may further comprise a plurality of electrical tracesindependently extending over the base to the plurality of heaters.

The optical scanning devices may comprise one or more optical elementsto allow for light to be projected by the optical scanning device. Forexample, an optical scanning device may optionally further comprise atleast one laser diode positioned on the base, such as at least one laserdiode that is optically coupled to the at least one optical waveguide.Optionally, the at least one laser diode may be positioned remotely fromthe base. For example, an optical scanning device may further comprisean optical fiber mechanically engaged with the base, such as an opticalfiber that is optically coupled to the at least one optical waveguide.In this way, the optical fiber may provide optical communication betweenthe at least one laser diode and the optical waveguide to allow lightfrom the at least one laser diode to be received by and transmitted orprojected from the optical waveguide. In embodiments, the at least oneoptical waveguide has a cross-sectional dimension less than or equal to10 microns. For example, the optical waveguide optionally has across-sectional width of between 1 and 10 microns, inclusive.Optionally, the optical waveguide has a cross-sectional height between 1and 10 microns, inclusive.

In some embodiments, an optical scanning system of provided. The opticalscanning system may comprise a resonantly oscillatable optical scanningmember, a first conductor disposed on the resonantly oscillatableoptical scanning member, a second conductor disposed adjacent to theresonantly oscillatable optical scanning member, and a capacitivesensing circuit. The capacitive sensing circuit may be coupled to thefirst conductor and the second conductor and may be configured togenerate a capacitance modulated signal that is modulated by a varyingcapacitance between the first conductor and the second conductor. Theoptical scanning system may further comprise an electrical signal tomechanical force transducer coupled to the resonantly oscillatableoptical scanning member. The electrical signal to mechanical forcetransducer may include an electrical signal input.

In some embodiments, the optical scanning system may further comprise aphase correction circuit coupled to the capacitive sensing circuit andto the electrical signal to mechanical force transducer. In someembodiments, the optical scanning system may further comprise a timingsignal generator coupled through the phase correction circuit to theelectrical signal to mechanical force transducer. The phase correctioncircuit may be configured to adjust a phase of a timing signal that isreceived from the timing signal generator to generate a phase adjustedtiming signal based, at least in part, on the capacitance modulatedsignal. The phase adjusted timing signal may be passed to the electricalsignal to mechanical force transducer. In some embodiments, the opticalscanning system may further comprise a light source optically coupled tothe resonantly oscillatable optical scanning member, and circuitry fordriving the light source. The circuitry for driving the light source maybe electrically coupled to the timing signal generator. In someembodiments, the phase correction circuit may comprise a phase detectioncircuit coupled to a phase shift circuit. The phase detection circuitmay be coupled to the capacitive sensing circuit. The phase shiftcircuit may include an input coupled to the timing signal generator andan output coupled to the electrical signal to mechanical forcetransducer.

In some embodiments, a source of imagewise modulated light may comprisethe optical scanning system described herein and may further comprise aframe buffer, a timing signal generator for generating a timing signal,read circuitry, and a phase correction circuit. The read circuitry maybe coupled to the frame buffer and the timing signal generator. The readcircuitry may be configured to read out pixel data from the frame bufferin a spiral pattern at times determined by the timing signal generator.The phase correction circuit may be coupled to the timing signalgenerator and the read circuitry and may be further coupled to thecapacitive sensing circuit. The phase correction circuit may beconfigured to adjust the timing signal based on the capacitancemodulated signal.

In some embodiments, a method of projecting an image is provided. Themethod comprises actuating a plurality of heaters of an optical scanningdevice to induce oscillation of a distal end of a cantilevered beam ofthe optical scanning device. The optical scanning device may comprise abase, the cantilevered beam, an optical waveguide, and a plurality ofheaters disposed on the cantilevered beam. The cantilevered beam mayextend from the base and include a proximal end attached to the base anda distal end. The optical waveguide may be positioned on the base andthe cantilevered beam and may extend from the base to the distal end ofthe cantilevered beam. The method further comprises actuating one ormore laser diodes to generate laser light. The one or more laser diodesmay be optically coupled to the optical waveguide. The laser light maybe transmitted from the optical waveguide at the distal end of thecantilevered beam to project an image.

In some embodiments, actuating the plurality of heaters may increasetemperatures of a plurality of regions of the cantilevered beam and mayinduce thermal expansion of the plurality of regions of the cantileveredbeam. The thermal expansion of the plurality of regions of thecantilevered beam may cause deflections of the distal end of thecantilevered beam corresponding to the oscillation. In some embodiments,the plurality of regions of the cantilevered beam correspond to quadrantsections.

In some embodiments, the one or more laser diodes may be opticallycoupled to the optical waveguide via one or more optical fibers that areoptically coupled to the one or more laser diodes and the opticalwaveguide. In some embodiments, the optical scanning device may furthercomprise a first capacitive sensing electrode disposed on thecantilevered beam and a second capacitive sensing electrode disposedadjacent to the cantilevered beam. The method may further comprisedetecting a capacitance signal corresponding to a capacitance betweenthe first capacitive sensing electrode and the capacitive sensingelectrode. The method may further comprise generating a phase calibratedtiming signal using a reference timing signal and a phase shift betweenthe reference timing signal and the capacitance signal. In someembodiments, the plurality of heaters may be actuated according to thephase calibrated timing signal and the one or more laser diodes may beactuated according to the reference timing signal. Alternatively, theplurality of heaters may be actuated according to the reference timingsignal and the one or more laser diodes may be actuated according to thephase calibrated timing signal.

In some embodiments, the oscillation may correspond to deflecting thedistal end of the cantilevered beam in a spiral pattern and the imagemay correspond to a two-dimensional image. In some embodiments,actuating the one or more laser diodes may include obtaining spiralpattern pixel data from a frame buffer, converting the spiral patternpixel data to one or more drive signals, and electrically coupling theone or more drive signals to the one or more laser diodes.

In some embodiments, an image projection system is provided. The imageprojection system comprises a resonantly oscillatable optical scanningmember including an optical waveguide for transmitting visible light.The system further comprises a first conductor disposed on theresonantly oscillatable optical scanning member. The system furthercomprises a second conductor disposed adjacent to the resonantlyoscillatable optical scanning member. The system further comprises acapacitive sensing circuit coupled to the first conductor and the secondconductor. The capacitive sensing circuit may be configured to generatea capacitance modulated signal that is modulated by a varyingcapacitance between the first conductor and the second conductor. Thesystem further comprises an electrical signal to mechanical forcetransducer coupled to the resonantly oscillatable optical scanningmember to induce oscillations of the resonantly oscillatable opticalscanning member. The system further comprises a timing signal generatorconfigured to output a timing signal. The system further comprises aphase correction circuit coupled to the capacitive sensing circuit andthe timing signal generator. The phase correction circuit may beconfigured to adjust a phase of the timing signal to generate a phaseadjusted timing signal based, at least in part, on the capacitancemodulated signal.

In some embodiments, the system further comprises a light sourceoptically coupled to the optical waveguide and circuitry for driving thelight source. The circuitry for driving the light source may beelectrically coupled to the timing signal generator to receive thetiming signal. Alternatively, the circuitry for driving the light sourcemay be electrically coupled to the phase correction circuit to receivethe phase adjusted timing signal. In some embodiments, the electricalsignal to mechanical force transducer may be electrically coupled to thetiming signal generator for inducing oscillations of the resonantlyoscillatable scanning member according to the timing signal.Alternatively, the electrical signal to mechanical force transducer maybe electrically coupled to the phase correction circuit for inducingoscillations of the resonantly oscillatable scanning member according tothe phase adjusted timing signal.

The optical scanning devices described herein may be used in a varietyof configurations. For example, the optical scanning devices may beuseful as a component of an augmented reality device, such as augmentedreality glasses comprising the optical scanning device and furthercomprising a transparent eyepiece optically coupled to the opticalscanning device. For example, the transparent eyepiece may be configuredto couple light received from the optical scanning device to an eyeposition defined in relation to the transparent eyepiece, while alsoallowing environmental light to pass through the transparent eyepiece tothe eye position.

In embodiments, the disclosed optical scanning devices may include othercomponents. For example, an optical scanning device may optionallyfurther comprise one or more side arms extending from the base andadjacent to a first side of the cantilevered beam. Optionally, one ormore capacitive sensing electrodes may be incorporated into an opticalscanning device. For example, an optical scanning device optionallyfurther comprises a first capacitive sensing metallization disposed onthe cantilevered beam and a second capacitive sensing metallizationdisposed on a side arm. The capacitive sensing metallizations maycorrespond to capacitive sensing electrodes, such as a first capacitivesensing electrode disposed on the cantilevered beam, and a secondcapacitive sensing electrode disposed adjacent to the cantilevered beam.

Capacitive sensing metallizations or electrodes may be useful forproviding feedback, such as in optical scanning systems comprising theoptical scanning device. Optionally, an optical scanning systemcomprises an optical scanning device including a first capacitivesensing electrode and a second capacitive sensing electrode; acapacitive sensing circuit coupled to the first capacitive sensingelectrode and the second capacitive sensing electrode; a timing signalgenerator; a phase detection circuit coupled to the timing signalgenerator and the capacitive sensing circuit, such as a phase detectioncircuit configured to receive a timing signal from the timing signalgenerator, to receive a varying capacitance modulated signal from thecapacitive sensing circuit, and to output a phase shift control signalat a phase shift control signal output; a phase shift circuit having atiming signal input coupled to the timing signal generator, a phasecontrol input coupled to the phase shift control signal output, and aphase adjusted signal output, such as a phase shift control circuit isthat configured to phase shift the timing signal by an amount inaccordance with the phase shift control signal to produce a phasecalibrated timing signal; a multiphase heating power signal generatorcoupled to the phase shift circuit, such as a multiphase heating powersignal generator that includes a plurality of heating signal outputsthat are coupled to the plurality of heaters disposed on thecantilevered beam and configured to receive the phase calibrated timingsignal from the phase shift circuit and to output, at the plurality ofheating signal outputs, a plurality of heating power signals that aretimed based on the calibrated timing signal.

It will be appreciated that the capacitive sensing techniques may beused in other optical scanning or projection systems generally. Forexample, in one embodiment, an optical scanning system comprises aresonantly oscillatable optical scanning member; a first conductordisposed on the resonantly oscillatable optical scanning member; asecond conductor disposed adjacent to the resonantly oscillatableoptical scanning member; a capacitive sensing circuit coupled to thefirst conductor and the second conductor and configured to generate acapacitance modulated signal that is modulated by a varying capacitancebetween the first conductor and the second conductor; and an electricalsignal to mechanical force transducer coupled to the resonantlyoscillatable optical scanning member, the electrical signal tomechanical force transducer including an electrical signal input.

Optionally, an optical scanning system may further comprise a phasecorrection circuit coupled to the capacitive sensing circuit and to theelectrical signal to mechanical force transducer; and a timing signalgenerator coupled through the phase correction circuit to the electricalsignal to mechanical force transducer. Optionally, the phase correctioncircuit is configured to adjust a phase of a timing signal that isreceived from the timing signal generator to generate a phase adjustedtiming signal based, at least in part, on the capacitance modulatedsignal. Optionally, the phase adjusted timing signal is passed to theelectrical signal to mechanical force transducer.

Useful optical scanning systems include those further comprising a lightsource optically coupled to the resonantly oscillatable optical scanningmember, and circuitry for driving the light source, such as circuitryfor driving the light source that is electrically coupled to the timingsignal generator. Optionally, the phase correction circuit comprises aphase detection circuit coupled to a phase shift circuit, such as aphase detection circuit that is coupled to the capacitive sensingcircuit, and a phase shift circuit that includes an input coupled to thetiming signal generator and an output coupled to the electrical signalto mechanical force transducer.

The optical scanning systems and optical scanning devices may be useful,in embodiments, as sources of imagewise modulated light. For example, asource of imagewise modulated light may correspond to a projectionsystem. Optionally, a source of imagewise modulated light comprises anoptical scanning system; a frame buffer; a timing signal generator forgenerating a timing signal; read circuitry coupled to the frame bufferand the timing signal generator, the read circuitry configured to readout pixel data from the frame buffer in a spiral pattern at timesdetermined by the timing signal generator; a phase correction circuitcoupled to the timing signal generator and the read circuitry andfurther coupled to the capacitive sensing circuit, such as a phasecorrection circuit that is configured to adjust the timing signal basedon the capacitance modulated signal.

Methods are also disclosed herein, such as methods of operating anoptical scanning system, an optical scanning device, or projecting oneor more images. Methods of this aspect may optionally comprise actuatinga plurality of heaters of an optical scanning device to induceoscillation of a distal end of a cantilevered beam of the opticalscanning device, such as an optical scanning device that comprises abase, a cantilevered beam, such as a cantilevered beam that extends fromthe base and includes a proximal end attached to the base and a distalend, an optical waveguide positioned on the base and the cantileveredbeam and extending from the base to the distal end of the cantileveredbeam, and a plurality of heaters disposed on the cantilevered beam; andactuating one or more laser diodes to generate laser light. Optionally,the one or more laser diodes are optically coupled to the opticalwaveguide. Optionally, the laser light is transmitted from the opticalwaveguide at the distal end of the cantilevered beam to project animage.

It will be appreciated that actuating the plurality of heaters mayincrease temperatures of a plurality of regions of the cantilevered beamand induce thermal expansion of the plurality of regions of thecantilevered beam. For example, the thermal expansion of the pluralityof regions of the cantilevered beam may cause deflections of the distalend of the cantilevered beam corresponding to the oscillation.Optionally, the plurality of regions of the cantilevered beam correspondto quadrant sections. It will be appreciated that the one or more laserdiodes may optionally be optically coupled to the optical waveguide viaone or more optical fibers that are optically coupled to the one or morelaser diodes and the optical waveguide or optionally positioned on thebase and directly optically coupled to the optical wave.

As described above, capacitive sensing electrodes may be useful asfeedback mechanisms to control the actuation of the heating elements andoptical sources (e.g. laser diodes). Optionally, an optical scanningdevice further comprises a first capacitive sensing electrode disposedon the cantilevered beam and a second capacitive sensing electrodedisposed adjacent to the cantilevered beam. For example, a method ofthis aspect may further comprise detecting a capacitance modulatedsignal corresponding to a capacitance between the first capacitivesensing electrode and the second capacitive sensing electrode; andgenerating a phase calibrated timing signal using a reference timingsignal and a phase shift between the reference timing signal and thecapacitance signal. Different actuation configurations may be usedincorporating the reference timing signal and the phase adjusted timingsignal. For example, the plurality of heaters are optionally actuatedaccording to the phase calibrated timing signal while the one or morelaser diodes are actuated according to the reference timing signal.Optionally, the plurality of heaters are actuated according to thereference timing signal and the one or more laser diodes are actuatedaccording to the phase calibrated timing signal.

As described above, the oscillation may corresponds to deflecting thedistal end of the cantilevered beam in a spiral pattern. The projectedimage may correspond to a two-dimensional image. To appropriatelyproject the image, various details may be used. For example, actuatingthe one or more laser diodes optionally includes obtaining spiralpattern pixel data from a frame buffer; converting the spiral patternpixel data to one or more drive signals; and electrically coupling theone or more drive signals to the one or more laser diodes.

The optical scanning systems and optical scanning devices describedherein may also be useful in image projection systems. Various aspectsdescribed herein may be useful in image projection systems generally.For example, an image projection system may comprise a resonantlyoscillatable optical scanning member including an optical waveguide fortransmitting visible light; a first conductor disposed on the resonantlyoscillatable optical scanning member; a second conductor disposedadjacent to the resonantly oscillatable optical scanning member; acapacitive sensing circuit coupled to the first conductor and the secondconductor and configured to generate a capacitance modulated signal thatis modulated by a varying capacitance between the first conductor andthe second conductor; an electrical signal to mechanical forcetransducer coupled to the resonantly oscillatable optical scanningmember to induce oscillations of the resonantly oscillatable opticalscanning member; a timing signal generator configured to output a timingsignal; and a phase correction circuit coupled to the capacitive sensingcircuit and the timing signal generator, such as a phase correctioncircuit that is configured to adjust a phase of the timing signal togenerate a phase adjusted timing signal based, at least in part, on thecapacitance modulated signal.

Useful image projection systems include those comprising a light sourceoptically coupled to the optical waveguide; and circuitry for drivingthe light source, such as circuitry for driving the light source that iselectrically coupled to the timing signal generator to receive thetiming signal or circuitry for driving the light source that iselectrically coupled to the phase correction circuit to receive thephase adjusted timing signal.

Useful resonantly oscillatable optical scanning members include acantilevered beam supporting an optical waveguide and a cantileveredoptical fiber. Useful electrical signal to mechanical force transducersinclude heaters positioned on a structure to induce thermal expansionand deflection by heating the structure as well as piezoelectricstructures that can induce physical expansion and deflection by exposingthe piezoelectric structures to a voltage. Optionally, the electricalsignal to mechanical force transducer is electrically coupled to thetiming signal generator for inducing oscillations of the resonantlyoscillatable scanning member according to the timing signal. Optionally,the electrical signal to mechanical force transducer is electricallycoupled to the phase correction circuit for inducing oscillations of theresonantly oscillatable scanning member according to the phase adjustedtiming signal.

The foregoing, together with other features and embodiments, will becomemore apparent upon referring to the following description, claims andaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a schematic illustration of a wearable augmented realitysystem embodiment.

FIG. 2 provides a schematic illustration of a wearable optical devicedepicting details of an optical projection system including an opticalscanning device, in accordance with some embodiments.

FIG. 3 provides a schematic illustration of an optical scanning deviceconfiguration according to some embodiments.

FIG. 4 provides a perspective schematic view of an optical scanningdevice, providing details of various device elements accordance withsome embodiments.

FIG. 5 provides a top plan schematic illustration of an optical scanningdevice accordance with some embodiments.

FIG. 6 provides a zoomed schematic view of a portion of an opticalscanning device accordance with some embodiments.

FIG. 7 provides a bottom plan schematic illustration of an opticalscanning device in accordance with some embodiments.

FIG. 8 provides a top plan schematic illustration of an optical scanningdevice accordance with some embodiments.

FIG. 9 provides a schematic illustration of components of an opticaldevice in accordance with some embodiments.

FIG. 10 provides a graphic overview of four separate heating elementsused, in embodiments, for driving an optical scanning device.

FIG. 11 provides a representative plot of heating power signals providedto four heating elements used, in embodiments, for driving an opticalscanning device in a circular or spiral configuration.

FIG. 12 provides a plot showing an example spiral path for a cantileverend in an optical scanning device.

FIG. 13 provides a plot showing examples of equally time-spaced pixelpositions along a spiral path.

FIG. 14 provides a plot FIG. 12 and FIG. 13 overlaid on one another.

FIG. 15 provides a block diagram representing components of a system fordriving an optical scanning device in accordance with some embodiments.

FIG. 16 provides a block diagram representing components of a system fordriving an optical scanning device in accordance with some embodiments.

FIG. 17 provides a flow diagram describing aspects of an opticalprojection method.

FIG. 18 provides a perspective schematic view of an optical scanningdevice in accordance with some embodiments.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Described herein are embodiments of optical scanners, optical projectionsystems, and methods of scanning optical waveguides and projectingimages. The disclosed devices and systems advantageously provide animprovement to the compactness, robustness, simplicity, and reliabilityof optical scanners and optical projection systems by implementing athermally driven actuator for inducing oscillations of a cantileverwithin the optical scanners and optical projection systems.

The disclosed devices may include a microscale optical scanning element,which may be exemplified, for example, as a microcantilever, alsoreferred to herein as a cantilever, a cantilevered beam, and the like. Acantilever may refer to a platform, beam, or other partially suspendedstructure that is supported by a base on only a single end, referred toherein as the proximal end, while the opposite end, referred to hereinas the distal end, is unsupported. The components of an optical scanningelement may be fabricated through techniques borrowed from the art ofmicrofabrication, including patterning, lithography, masking, etching,liftoff, deposition, and other techniques.

Advantageously, the optical scanning elements may include crystallineand/or polycrystalline materials. In some embodiments, components of anoptical scanning element, such as a microcantilever and supporting base,may be fabricated from materials having relatively high thermalconductivities, such as silicon, silicon carbide, diamond, and the like.Example useful thermal conductivities include those greater than about50 W/m⋅K, selected from the range of 50 W/m⋅K to 2500 W/m⋅K, or selectedfrom the range of 100 W/m⋅K to 500 W/m⋅K. The use of materials havinghigh thermal conductivities may be advantageous for more quicklydissipating heat introduced by a thermal actuator.

Materials useful in the optical scanning elements described herein mayfurther exhibit non-zero coefficients of thermal expansion to allowcantilevered beams to deflect when regions of the cantilevered beams areheated. Example linear coefficients of thermal expansion useful withvarious embodiments include those having values greater than 1×10⁻⁶/K,selected from the range of 1×10⁻⁶/K to 50×10⁻⁶/K, or selected from therange of 1×10⁻⁶/K to 10×10⁻⁶/K.

Other materials may be incorporated into optical scanning elementsdescribed herein for various purposes. For example, metals may beincorporated as electrically conducting elements or resistive heatingelements, for example. For example, copper, aluminum, gold, and/orsilver may be useful as conductive materials. Other low resistivitymaterials may be similarly useful, such as doped silicon, doped siliconcarbide, etc. Certain materials may be useful as heating elements, suchas platinum, low doped silicon, silicon oxide, silicon nitride, metaloxides, etc. In embodiments, these materials may exhibit suitableelectrical resistivity to allow for useful generation of heat atspecific locations by passing a current through the material.

The disclosed optical scanning elements may exhibit any suitablecharacteristic resonant frequencies in the cantilevered beam, such asbetween 20 kHz to 250 kHz, depending on the application and constructionof the devices. In some embodiments, a characteristic resonant frequencyof about 62 kHz may be employed. Sizes of the cantilevered beam scannercomponents may dictate the characteristic resonant frequencies. Suitabledimensions of a cantilevered beam may include a thickness of between 50μm and 250 μm, a width of between 50 μm and 250 μm, and a length of 500μm to 2000 μm. Example dimensions for a cantilevered beam include about100 μm in width, about 100 μm in thickness, and about 1000 μm in length.

The optical scanners and optical projection systems described herein maybe useful, for example, in wearable augmented reality systems, such asaugmented reality glasses that incorporate transparent eyepieces toallow both light from the environment and light generated by an opticalprojection system to reach a user's eye. FIG. 1 provides a schematicillustration of a wearable augmented reality system 100 including aframe 105. Light generated by an optical projection system (not shown inFIG. 1) is received by an input optical element 110, which directs lightthrough a first pupil expansive optical element 115 and a second pupilexpansive optical element 120 to direct at least a portion of theprojected light to user eye positions 125.

The input optical element 110, the first pupil expansive optical element115, and the second pupil expansive optical element 120 are componentsof an eyepiece 117. The eyepiece 117 may include a transparent materialand the input optical element 110, the first pupil expansive opticalelement 115, and the second pupil expansive optical element 120 may takethe form of surface relief or volume micro-optical elements, such asgratings. It will be appreciated that the eye positions 125 represent anapproximate location of a user's eye in order for the user's eyes toreceive light from both the frame 105 and from the environment, as thepupil expansive optical elements 115 and 120 are at least partiallytransmissive in the visible spectral region. Details of theconfiguration of wearable augmented reality systems and associatedcomponents are further described in U.S. Provisional Patent ApplicationNo. 62/377,831, filed on Aug. 22, 2016, and U.S. Non-provisional PatentApplication Nos. 15/683,412, 15/683,624, 15/683,638, 15/683,644,15/683,702, and 15/683,706, filed on Aug. 22, 2017. These applicationsare hereby incorporated by reference in their entireties.

Further details of the augmented reality system 100 are schematicallydepicted in FIG. 2, which depicts frame 105, a fiber optic 230, one ormore mechanical supports 235, a cantilevered optical scanner 240, acollimating and coupling optic 245, and various optical elementsincluding input optical element 110 and pupil expansive optical elements115 and 120.

FIG. 3 provides a schematic illustration of cantilevered optical scanner240. Cantilevered optical scanner 240 includes a base 305 and acantilevered beam 310. Optionally base 305 and cantilevered beam 310 areintegrally and monolithically formed and represent different portions ofa single device element. For example, base 305 may be attached toanother substrate or support component, while cantilevered beam 310 maybe attached to base 305 at a proximal position and freestanding (i.e.,unsupported) at a distal position. Cantilevered beam 310 is depicted inFIG. 3 as supporting an optical waveguide 315 to couple light from aninput element to a collimating and coupling optic 245, which may allowfor collimating and redirecting incident light. Base 305 may support orbe constructed to include a v-groove 320, which may correspond to amechanical coupling element to position an optical fiber at a locationto optically couple the core of the optical fiber to the opticalwaveguide 315. Light from the optical waveguide 315 is directed tocoupling optic 245, where it is collimated and directed to other opticalcomponents, such as input optical element 110 of augmented realitysystem 100. Linearly polarized light from the optical waveguide 315enters an input surface 325 of the coupling optic 245, is transmittedthrough a polarization beam splitter (PBS) 330 and reaches a quarterwave plate (QWP) 335. According to alternative embodiments, the lightmay be s-polarized or p-polarized as judged at incidence on the PBS 330.Upon passing through the QWP 335 the polarization state of the light isconverted from linearly polarized to circularly polarized light (e.g.,according to alternative embodiments the circularly polarized light maybe RHCP or LHCP dependent on the orientation of the QWP). The light isthen reflected by a concave mirror 340. Upon reflection the circularpolarized state of the light is reversed (i.e. switched from RHCP toLHCP or vice versa). Thereafter upon once again passing through the QWP335 the light will be changed to a linear polarization state that isperpendicular to the initial linear polarization state and thereforewill be reflected by the PBS 330 down toward an exit surface 345. Uponpassing through the exit surface 345 the light, now collimated, willenter the input optical element 110. The collimated light will beredirected by the input optical element and the pupil expansive opticalelements 115 and 120 to user eye positions 125. Light entering the inputoptical element 110 takes the form of a beam of light the angle of whichis varied according to the instantaneous position of the distal tip ofthe optical waveguide 315. Each angle of the beam corresponds an imagepixel defined in angular coordinates. The first pupil expansive element115 incrementally redirects light down (in the perspective of FIG. 1)toward the second pupil expansive optical element 120 thereby increasinga horizontal width of the beam. The second pupil expansive opticalelement 120 incrementally redirects light out, generally towards theuser eye position, thereby increasing the vertical height of the beam.It will be appreciated that some light may also be directed outward awayfrom the user eye position. Expansion of the horizontal width andvertical height fills an eyebox which provides a tolerance for movementof the user's pupil while maintaining visibility of the output imagery.

FIG. 4 provides a perspective schematic view of an optical scanningdevice 400.

Optical scanning device 400 includes base 405 and cantilevered beam 410.Base 405 includes a v-groove 415 for positioning an optical fiber 420,such as a lensed optical fiber, at a position for optical communicationbetween a core of optical fiber 420 and an optical waveguide 425. Base405 also includes electrical contacts 430, arranged in electricalcommunication with other elements, including heating elements 435disposed on cantilevered beam 410. A chassis 440 surrounds othercomponents and may be used to support base 405 and optical element 445and ensure proper positioning of optical element 445 with respect tocantilevered beam 410 and optical waveguide 425. Optical scanning device400 is illustrated in FIG. 4 as including position sensing contacts 450and 465, which may be useful for sensing the distance betweencantilevered beam 410 and position sensing contact 450, such as by wayof time-dependent capacitance measurements between position sensingcontact 450 and position sensing contact 465, to provide positioninformation for cantilevered beam 410.

FIG. 5 provides a top plan schematic view of optical scanning device500. Optical scanning device 500 is similar to and/or may correspond tooptical scanning device 400 depicted in FIG. 4. In one example, opticalscanning device 500 may be a 62 kHz MEMS resonant spiral opticalscanner. Optical scanning device 500 includes base 505 and cantileveredbeam 510. Base 505 includes a v-groove 515 for positioning an opticalfiber 520 at a position for optical communication between a core ofoptical fiber 520 and an optical waveguide 525. Base 505 also includeselectrical contacts 530, arranged in electrical communication with otherelements, such as heating elements 535 disposed on cantilevered beam510. Optical scanning device 500 is illustrated in FIG. 5 as includingextensions 545, which are positioned adjacent to cantilevered beam 510,with extensions 545 including sensing electrodes 550, which may beuseful for time-dependent capacitance measurements, as described aboveand below with reference to FIG. 15.

FIG. 6 provides a zoomed perspective view of an optical scanning device600. Optical scanning device 600 is similar to and/or may correspond tooptical scanning devices 400 and 500 depicted in FIGS. 4 and 5. Opticalscanning device 600 is shown with an end of optical fiber 620 engaged inv-groove 615 and positioned in alignment with and/or optically coupledto optical waveguide 625. Electrical traces 630 are shown providingelectrical connections to heating elements 635 positioned oncantilevered beam 610.

FIG. 7 provides a bottom plan view schematic illustration of an opticalscanning device 700. Optical scanning device 700 is similar to and/ormay correspond to optical scanning devices 400, 500, and 600 depicted inFIGS. 4-6. Optical scanning device 700 includes base 705 andcantilevered beam 710. Optical scanning device 700 is illustrated inFIG. 7 as including a sensing contact 750, which may be useful foridentifying the distance between cantilevered beam 710 and positionsensing contacts (not visible in FIG. 7) on top sides of extensions 745,such as by way of time-dependent capacitance measurements, to provideposition information for cantilevered beam 710. Electrical traces 730are shown, providing electrical connections to heating elements 735 andsensing contact 750 positioned on cantilevered beam 710.

FIG. 8 provides a top plan view schematic illustration of an opticalscanning device 800. Optical scanning device 800 is similar to opticalscanning devices 400, 500, 600, and 700 depicted in FIGS. 4-7, butoptical scanning device 800 includes local optical sources. Opticalscanning device 800 includes base 805 and cantilevered beam 810. Insteadof a v-groove and optical fiber, optical scanning device 800 includes aplurality of optical sources 815A, 815B, and 815C on base 805, which maycorrespond to different color (e.g., red, green, and blue) laser diodes,for example. Alternatively, the number of optical sources may beincreased beyond three to increase brightness, or, in the case wheremore than three emission wavelengths are provided, to increase colorgamut. It will be appreciated that, in some embodiments, both an opticalfiber and a local optical source may be incorporated into an opticalscanning device.

Optical scanning device 800 is illustrated in FIG. 8 as includingposition a sensing contact 845, which may be useful for identifying thedistance between cantilevered beam 810 and a position sensing contacts(not visible in FIG. 8) on a bottom side of the cantilevered beam 810,such as by way of time-dependent capacitance measurements, to provideposition information for cantilevered beam 810. Electrical contacts 830are shown, providing electrical conductivity to heating elements 835 andsensing contact 845. A plurality of waveguides 825A, 825B and 825C aredepicted in FIG. 8. Waveguide 825A is positioned on optical scanningdevice 800 and extends from base 805 to the distal end of cantileveredbeam 810, and in direct optical communication with optical source 815A.Waveguides 825B and 825C are shown as positioned on base 805 and indirect optical communication with optical sources 815B and 815C,respectively. Optionally, waveguides 825B and 825C may extend from base805 to the distal end of cantilevered beam 810, similar to waveguide825A. However, in the configuration depicted in FIG. 8, directionaloptical coupling is employed, where the spacing and length of adjacentportions between optical waveguides 825A and 825B and between opticalwaveguides 825A and 825C are selected so as to transfer the light inoptical waveguide 825B to optical waveguide 825A and to transfer thelight in optical waveguide 825C to optical waveguide 825A, for exampleby evanescent coupling.

FIG. 9 provides a schematic illustration of an eyepiece arrangement 900,which may be used as an alternative to the configuration depicted inFIG. 1, for example. In arrangement 900, optical scanning device 905directly projects light 910 onto first optical element 915, which maydirect at least a portion of light 910 from optical scanning device 905to user eye position 920. Second optical element 925 may allow light 930from the environment to directly pass to user eye position 920 to allowfor the projected light 910 from optical scanning device to appearoverlaid on and/or within the environmental light 930 for augmentedreality viewing. Light from the optical scanning device 905 undergoestotal internal reflection (TIR) at a gap 935 between the first opticalelement 915 and the second optical element 925, whereas light from theenvironment, due to its different incidence angular range, passesthrough the gap 935 and reaches the user eye position 920.

It will be appreciated that multiple independent heating elements areincluded in the optical scanning devices depicted in FIGS. 4-8.Optionally, four heating elements are included in the optical scanningdevice, such as two heating elements on a top surface of a cantileveredbeam and two heating elements on a bottom surface of a cantileveredbeam. FIG. 10 provides a graphic overview of an electrical configurationof four heating elements used for inducing oscillations in an opticalscanning device. In FIG. 10, heating elements 1005, 1010, 1015, and 1020are positioned in independent electrical communication with a quadratureheating power signal source 1025.

FIG. 11 provides a representative plot of heating power signals 1105,1110, 1115, and 1120, provided to the four heating elements for drivingan optical scanning device in a circular or spiral pattern. The heatingpower signals are shown having a characteristic repetition rate andamplitude, which may vary depending on the magnitude of oscillationdesired to be imparted. The phases of the heating power signals 1105,1110, 1115, and 1120 are shifted by 90 degrees, which may provide forgenerating successive progressions of deflections of a cantilevered beamto generate an overall circular or spiral motion, for example.

It will be appreciated that the magnitude and duration of the heatingpower signals depicted in FIG. 11 are representative and forillustrative purposes and that the heating power signals may be the sameas or different from those in FIG. 11. In general, the heating powersignals may generally correspond to a form having a repetition frequencymatching the resonant frequency of a cantilever beam. For example, theheating power signals may each correspond to a square wave of ¼ of theduration of the repetition period, as illustrated in FIG. 11, or to asquare wave of longer than or less than ¼ of the duration of therepetition period. Optionally, the heating power signals may correspondto a pulse (e.g., a Gaussian shaped pulse), a triangular wave, or othernon-square wave. Moreover, the magnitude of the heating power signalsmay be varied as a function of time to induce varied deflections in acantilevered beam, which may be useful for generating a spiral or otherdeflection pattern of the distal end of the cantilevered beam.Additionally signals of constant amplitude can add energy to thecantilevered beam during successive pulse periods whereby the radialcoordinate of the spiral pattern progressively increases from onewaveform period to the next, until frictional losses equal the rate atwhich the pulsed signals add energy to the spiral oscillation. Once apredetermined maximum radial coordinate is achieved, the phase of thedrive signals may be shifted by 180° to bring the cantilever beam backto its center position. Alternatively the cantilevered beam's orbit maybe allowed to decay back to zero.

The optical scanning devices disclosed herein are useful in projectionsystems, such as to generate and project images or sequences of imagesto represent an animation or motion picture. By repeating a spiraloscillation and outputting different images, a frame-by-frame imageprojection may be generated. Various implementations of a projectionsystem are useful with the optical scanning devices described herein,and by controlling the light being output and projected by the opticalscanning device as a function of the position of the scanning device,any desirable image can be projected.

For example, FIG. 12 depicts a sample spiral scan pattern, which mayrepresent the position of a distal end of a cantilevered beam or thelocation of a projected beam of light exiting from an optical waveguideat the distal end of the cantilevered beam. It will be appreciated thatthe depicted spiral scan pattern is merely exemplary and that other scanpatterns may be useful with various embodiments. For example, the spiralscan pattern may represent a center to periphery scan direction or aperiphery to center scan direction. Additionally, such scan patterns maybe clockwise or counterclockwise. FIG. 13 depicts positions of locationsequally spaced in time of a distal end of a cantilevered beamoscillating according to the spiral scan pattern depicted in FIG. 12 ora positions of a beam of light projecting from an optical waveguide onthe cantilevered beam. The depictions in FIGS. 12 and 13 are illustratedoverlaid on one another in FIG. 14. Use of such a scan pattern andprojection positions may allow for projection of an image, or series ofimages upon repetition of the spiral scan pattern.

It will be appreciated that the position locations depicted in FIG. 13may correspond to pixel output locations. Note that the coupling optic245 maps each position to a specific angle of a collimated beam that isoutput by the coupling optic 245, so that each pixel is described byangular coordinates in the field of view produced by the eyepieces 117.The pixels making up digital images and digital frames of a video arecommonly stored in a rectangular grid of pixels in a raster graphicstructure, which may not be directly compatible with the pixel outputlocations depicted in FIG. 13 and may require for reading particularpixels near the center of an image first and pixels near the peripherylater. In addition, pixel interpolation and manipulation of the pixelsin a raster graphic structure may be necessary for the image projectedin a spiral scan pattern to appear the same as that stored in the rastergraphic structure. For example, the x-y addresses of pixels needed to beoutput by a spiral scan projection system like those disclosed hereinmay be obtained by use of a spiral scan address sequence generator. Arandom access read circuit may aid in obtaining the corresponding pixelinformation from a frame buffer storing pixels in a raster graphicstructure. The digital pixel information may be converted to one or moreanalog values, which may be then amplified, for driving one or morelight sources, such as laser diodes, to provide appropriate intensitiesfor output.

To correctly project the image, the pixel information and output lightintensities will need to be matched in time with the projection locationof the output light, which is dictated by the position of the distal endof the cantilevered beam in the optical projection system. It will beappreciated that one or more phase delays between a source timing signalmay be encountered due to the components of the optical projectionsystem. For example, a phase delay may be introduced in one or more ofthe processes of reading pixel information according to a spiral scanaddress sequence, digital pixel to analog laser drive signal conversion,and laser drive signal amplification. Additional phase delays may beintroduced during the process of oscillating the cantilevered beam,which may arise from drive electronics associated with generating aheating power signal, or with the process of heating the portions of thecantilevered beam to generate a deflection of the cantilevered beam.Accordingly, as described further herein below, tracking a position ofthe cantilevered beam, such as by way of capacitance measurements, mayallow for correction and/or compensation of all the various phase delaysthat may be introduced.

FIGS. 15 and 16 depict block diagrams representing components of systemsfor driving optical scanning devices that incorporate a phase correctioncircuit to compensate for phase delays introduced during projection ofan image. In FIG. 15, the phase delay is corrected on the mechanicalside, where a phase adjusted signal is provided to a mechanical forcetransducer is coupled to a cantilevered beam (i.e., heating elements inthermal communication with the cantilevered beam). In FIG. 16, the phasedelay is corrected on the optical side, where a phase adjusted signal isprovided to a pixel sequence address generator used to obtain pixelinformation for projection.

In FIG. 15, system 1500 includes a timing signal generator 1505 thatprovides a timing signal to spiral scan address sequence generator 1510.The address sequence generated by spiral scan address sequence generator1510 is provided to random access read circuit 1515 which obtains pixelinformation from a frame buffer 1520 according to the address sequence.Frame buffer 1520 optionally resides within a graphics processing unit1525. The random access read circuit 1515 provides digital pixelinformation for three colors (e.g., red, green, and blue) to digital toanalog converters 1530A, 1530B, and 1530C, which provide analog outputsto laser drive amplifiers 1535A, 1535B, and 1535C to providecurrent/voltage to laser diodes 1540A, 1540B, and 1540C. The laserdiodes output light that is coupled to a waveguide on a thermally drivencantilever supported waveguide scanner 1545 for projection. It will beappreciated that other resonantly oscillatable optical scanning membersbesides a cantilever supported waveguide scanner may be used, such as afree-ended optical fiber.

To position the cantilever to the appropriate position for outputting aparticular pixel value, a quadrature phased heating power signalgenerator 1550 outputs heating signals for driving heating elements 1555on the thermally driven cantilever supported waveguide scanner 1545. Itwill be appreciated that other electrical signal to mechanical forcetransducers may be used in place of the thermally driven cantilever,such as a piezoelectric based system or an electromagnetic based system.

A capacitive sensing circuit 1560 is positioned to detect a capacitancevalue representative of a position of the cantilever. It will beappreciated that position sensing circuitry and components may be usedin place of capacitive sensing circuit, such as a piezoresistor- orstrain-sensor-based circuit. The capacitance value from capacitivesensing circuit 1560 is provided to a phase detection circuit 1565 of aphase correction circuit 1570, which also receives the source timingsignal from timing signal generator 1505. A phase shift circuit 1575 ofthe phase correction circuit 1570 also receives source timing signalfrom timing signal generator 1505 and generates a phase adjusted timingsignal that is provided to quadrature phased heating power signalgenerator 1550 to appropriately position the cantilever.

In FIG. 16, system 1600 includes a timing signal generator 1605 thatprovides a timing signal to a drive signal generator 1610 for generatingone or more electrical signals provided to one or more electrical signalto mechanical force transducers 1615 for mechanically oscillating aresonantly oscillatable optical scanning member 1620. It will beappreciated that electrical signal to mechanical force transducers 1615may correspond to resistive heating elements used to induce oscillationresonantly oscillatable optical scanning member 1620, as describedabove, and that other electrical signal to mechanical force transducersmay be used, such as piezoelectric or electromagnetic elements. Inaddition, it will be appreciated that resonantly oscillatable opticalscanning member 1620 may correspond to a cantilevered beam having one ormore optical waveguides thereon, as described above, and that otherresonantly oscillatable optical scanning members may be used, such as afree-ended (cantilevered) optical fiber.

A position sensing circuit 1625 is used to identify a position of theresonantly oscillatable optical scanning member and provide positionfeedback to a phase detection circuit 1630 of a phase correction circuit1635, which also receives the source timing signal from timing signalgenerator 1605. It will again be appreciated that position sensingcircuit 1625 may correspond to a capacitance sensing circuit, asdescribed above, and that other position sensing circuits may be used,such as a piezoresistor- or strain-sensor-based position sensingcircuit. A phase shift circuit 1640 of the phase correction circuit 1635also receives source timing signal from timing signal generator 1605 togenerate a phase adjusted timing signal.

The phase adjusted timing signal is provided to additional circuitry forappropriately driving optical elements to output a suitable pixel valuebased on the position of the resonantly oscillatable optical scanningmember 1620. As illustrated, the phase adjusted timing signal isprovided to spiral scan address sequence generator 1645. The addresssequence generated by spiral scan address sequence generator 1645 isprovided to random access read circuit 1650, which obtains pixelinformation from a frame buffer 1655 according to the address sequence.Frame buffer 1655 optionally resides within a graphics processing unit1660. The random access read circuit 1650 provides digital pixelinformation for three colors (e.g., red, green, and blue) to digital toanalog converters 1665A, 1665B, and 1665C, which provide analog outputsto laser drive amplifiers 1670A, 1670B, and 1670C to providecurrent/voltage to laser diodes 1675A, 1675B, and 1675C. The laserdiodes output light that is coupled to resonantly oscillatable opticalscanning member 1620 for projection.

FIG. 17 provides a flow diagram providing an overview of a method 1700of projecting an image. It will be appreciated that the blocksidentified in FIG. 17 may correspond to operations of a method and maybe performed in the specific order identified in FIG. 17 or in any otherorder. Optionally, blocks in FIG. 17 may be performed simultaneously orsequentially. Additionally, each of the blocks in FIG. 17 may beoptionally and independently repeated one or more times.

At block 1705, an optical scanning device is provided, such as anoptical scanning device comprising a base, a cantilevered beam extendingfrom the base and including a proximal end attached to the base and afree distal end, an optical waveguide positioned on the base and thecantilevered beam and extending from the base to the distal end of thecantilevered beam, and a plurality of heaters disposed on thecantilevered beam. It will be appreciated that the optical scanningdevice can include other components than those specified above,including an optical source, which may correspond to an optical fiberpositioned in optical communication with a laser diode, for example, ora laser diode directly in optical communication with the opticalwaveguide. In addition, electrical traces or electrodes may be includedin the optical scanning device, such as to provide electricalconnectivity to the plurality of heaters. Optionally, the opticalscanning device may include one or more capacitive sensingmetallizations disposed on the cantilevered beam or adjacent to thecantilevered beam, such as on a side arm.

At block 1710, the plurality of heaters are actuated to induceoscillation of the distal end of the cantilevered beam of the opticalscanning device. As described above, the plurality of heaters may eachbe actuated in sequence to induce a desired oscillation. For example,the heaters may be actuated using electrical signals similar to thosedepicted in FIG. 11 to induce a spiral shaped oscillation. It will beappreciated that actuating the plurality of heaters may increasetemperatures of a plurality of regions of the cantilevered beam toinduce thermal expansion of the plurality of regions, such as quadrantsections, and cause deflection of the distal end of the cantileveredbeam. Use of materials with high thermal conductivity, such as silicon,silicon carbide, or diamond may be useful to allow the heat generated toquickly dissipate through thermal conduction once the desired deflectionis created. Oscillations of any desired frequency may be induced, thoughoscillations having a frequency matching the natural resonant frequencyof the cantilevered beam may be most desirable.

At block 1715, one or more laser diodes are actuated to generate laserlight that is optically coupled to the optical waveguide of the opticalscanning device for projection therefrom. As described above, the one ormore laser diodes may be directly included on the base of the opticalscanning device. Optionally the one or more laser diodes are locatedremote from the base of the optical scanning device but are in opticalcommunication with the optical waveguide, such as by way of one or moreintermediate optical waveguides and/or optical fibers.

It will be appreciated that blocks 1710 and 1715 may be repeated asdesired to generate multiple projections in sequence. For example, theone or more laser diodes may be actuated multiple times as thecantilevered beam oscillates to generate a spatial sequence of projectedlight. Similarly, the plurality of heaters may be actuated multipletimes to maintain oscillation of the cantilevered beam in a desiredpattern, such as to allow multiple spiral oscillations in sequence tooccur. In some embodiments, the oscillations are allowed to dampen sothat the cantilevered beam can return to a neutral position beforebeginning the next oscillation.

As noted above, the optical scanning device may include multiplecapacitive sensing metallizations, which may also be referred to hereinas capacitive sensing electrodes. As depicted in block 1720, the methodmay optionally comprise detecting a capacitance signal corresponding toa capacitance between the capacitive sensing electrodes. For acapacitance between a first capacitive sensing electrode disposed on thecantilevered beam and a second capacitive sensing electrode disposedadjacent to the cantilevered beam, the capacitance may be modulated asthe cantilevered beam oscillates and may be representative of aproximity between the capacitive sensing electrodes and/or the positionof the cantilevered beam. The capacitance may be sensed by coupling anAC voltage signal between the first and second capacitance sensingelectrode and sensing the amplitude of the signal that is coupledthrough. The capacitance between the first and second capacitancesensing electrodes may be included in a voltage divider, in series witha fixed impedance. The frequency of the sensing signal may be selectedto be far from a resonant frequency of the cantilevered beam. The phasedetection circuit (1565, FIG. 15, or 1630, FIG. 16) may include anenvelope detector or a demodulator to process the signal coupled betweenthe first and second capacitance sensing electrodes in order to obtain acapacitance modulated signal having a frequency corresponding to theoscillation of the cantilevered beam.

As described above the laser diode may output light while thecantilevered beam is oscillating and the position of the cantileveredbeam may dictate the direction and position where the light isprojected. In order for the projected light to be positioned correctlyto display an image (e.g., a sequence of projected pixels), the positionof the cantilevered beam must be appropriately matched to thecorresponding light output (e.g., color and intensity distribution). Foroscillations of the cantilevered beam in a spiral, a spiral patternpixel data information may be obtained from a frame buffer and the pixeldata may be converted to one or more drive signals provided to the oneor more laser diodes. If the plurality of heaters and laser diodes areactuated using the same timing signal, the position of the cantileveredbeam and the light output may be out of sequence due to one or moredelays incurred in the system. Having position information about thecantilevered beam, such as by way of the capacitance signal, may allowthis delay to be accommodated. Thus, the capacitance signal mayoptionally be used, such as shown at block 1725, to generate a phasecalibrated timing signal, such as by identifying a phase shift betweenthe capacitance signal and a reference timing signal.

Two different configurations of the phase calibrated and referencetiming signal may be used. For example, the plurality of heaters may beactuated according to the reference timing signal while the one or morelaser diodes are actuated according to the phase calibrated timingsignal. Alternatively, the one or more laser diodes may be actuatedaccording to the reference timing signal while the plurality of heatersare actuated according to the phase calibrated timing signal. In eitherof these ways, delays can be accommodated to allow for correctprojection of an image where the position of the cantilevered beam andgeneration of laser light are correctly timed.

Other configurations and features of the cantilevered beam and opticalscanning device are contemplated. For example, FIG. 18 depicts aperspective schematic illustration of another optical scanning device1800. Optical scanning device 1800 includes base 1805 and cantileveredbeam 1810. Base 1805 includes a v-groove 1815 for positioning an opticalfiber 1820, such as a lensed optical fiber, at a position for opticalcommunication between a core of optical fiber 1820 and an opticalwaveguide 1825 supported on a top surface of cantilevered beam 1810.Base 1805 also includes electrical contacts 1830, arranged in electricalcommunication with other elements, including heating elements 1835disposed on a top side of cantilevered beam 1810. Additional heatingelements 1835 (not visible in FIG. 18) may be positioned on a bottomside of cantilevered beam 1810. Additional electrical contacts 1830 (notvisible in FIG. 18), may be also positioned on a bottom side of base1805, such as to provide electrical connections to heating elements 1835positioned on the bottom side of cantilevered beam 1810 and to positionsensing contact 1840 located near a distal end of cantilevered beam1810.

As illustrated, heating elements 1835 are located at a proximal end ofcantilevered beam 1810, near to base 1805, while optical waveguide 1825extends from base 1805 and the proximal end of cantilevered beam 1810 toa distal end of cantilevered beam 1810. In addition, cantilevered beam1810 has a tapered width and/or thickness. For example, proximal end ofcantilevered beam 1810 has a thickness that is greater than thethickness of cantilevered beam 1810 at the distal end. Similarly,proximal end of cantilevered beam 1810 has a width that is greater thanthe thickness of cantilevered beam 1810 at the distal end. It will beappreciated that tapering the cross-sectional dimension(s) of thecantilevered beam by reducing a width and/or thickness dimension ofcantilevered beam 1810 in this way may allow for an increase in theresonant frequency of cantilevered beam 1810. Increasing the resonantfrequency of cantilevered beam 1810 may be useful, for example, inincreasing the rate at which oscillations occur in the cantilevered beam1810. In embodiments, such an increased resonant frequency may allow foran optical projector employing optical scanning device 1800 to have ahigher frame rate.

Optical scanning device 1800 is illustrated in FIG. 18 as includingposition sensing contacts 1840 on extensions 1845 and position sensingcontact 1850 on cantilevered beam 1810, which may be useful for sensingthe distance between cantilevered beam 1810 and position sensingcontacts 1840, such as by way of time-dependent capacitance measurementsbetween position sensing contacts 1840 and position sensing contact1850, to provide position information for cantilevered beam 1810. Asillustrated in FIG. 18, position sensing contacts 1840 are positioned ona side surface and a top surface near the distal end of extensions 1845.Optionally, position sensing contacts 1840 may be positioned on a bottomsurface of extensions 1845 in addition to or alternative to positioningon a top surface. Position sensing contact 1850 is depicted aspositioned on a side surface of cantilevered beam 1810 and may furtherbe positioned on a bottom surface of cantilevered beam 1810.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed. Thus, it will be understood that although thepresent invention has been specifically disclosed by preferredembodiments and optional features, modification and variation of theconcepts herein disclosed may be resorted to by those skilled in theart, and that such modifications and variations are considered to bewithin the scope of this invention as defined by the appended claims.

What is claimed is:
 1. A method comprising: providing an opticalscanning device, the optical scanning device comprising a base, acantilevered beam extending from the base, and a plurality of heatersdisposed on the cantilevered beam; actuating the plurality of heaters toinduce oscillation of the cantilevered beam; and actuating a lightsource to generate light that is coupled to an optical waveguide that ispositioned on the base and the cantilevered beam and extends from thebase along the cantilevered beam.
 2. The method of claim 1, wherein thecantilevered beam includes a proximal end attached to the base and adistal end, and wherein actuating the plurality of heaters inducesoscillation of the distal end of the cantilevered beam.
 3. The method ofclaim 2, wherein the plurality of heaters are disposed on thecantilevered beam proximate to the proximal end.
 4. The method of claim1, wherein the optical scanning device includes one or more capacitivesensing electrodes disposed on the cantilevered beam or adjacent to thecantilevered beam.
 5. The method of claim 4, further comprising:detecting a capacitance signal corresponding to a capacitance betweenthe capacitive sensing electrodes, wherein the capacitance isrepresentative of a position of the cantilevered beam.
 6. The method ofclaim 1, wherein the light source is a laser diode, and wherein thelight is a laser light.
 7. The method of claim 1, wherein the pluralityof heaters comprise four heaters.
 8. The method of claim 1, wherein theplurality of heaters are spaced about the cantilevered beam.
 9. Themethod of claim 1, wherein the cantilevered beam has a top side and abottom side.
 10. A non-transitory computer-readable medium comprisinginstructions that, when executed by one or more processors, cause theone or more processors to perform operations comprising: actuating aplurality of heaters to induce oscillation of a cantilevered beam of anoptical scanning device, wherein the optical scanning device comprises abase, the cantilevered beam extending from the base, and the pluralityof heaters disposed on the cantilevered beam; and actuating a lightsource to generate light that is coupled to an optical waveguide that ispositioned on the base and the cantilevered beam and extends from thebase along the cantilevered beam.
 11. The non-transitorycomputer-readable medium of claim 10, wherein the cantilevered beamincludes a proximal end attached to the base and a distal end, andwherein actuating the plurality of heaters induces oscillation of thedistal end of the cantilevered beam.
 12. The non-transitorycomputer-readable medium of claim 10, wherein the optical scanningdevice includes one or more capacitive sensing electrodes disposed onthe cantilevered beam or adjacent to the cantilevered beam.
 13. Thenon-transitory computer-readable medium of claim 12, wherein theoperations further comprise: detecting a capacitance signalcorresponding to a capacitance between the capacitive sensingelectrodes, wherein the capacitance is representative of a position ofthe cantilevered beam.
 14. The non-transitory computer-readable mediumof claim 10, wherein the light source is a laser diode, and wherein thelight is a laser light.
 15. A system comprising: one or more processors;and a computer-readable medium comprising instructions that, whenexecuted by the one or more processors, cause the one or more processorsto perform operations comprising: actuating a plurality of heaters toinduce oscillation of a cantilevered beam of an optical scanning device,wherein the optical scanning device comprises a base, the cantileveredbeam extending from the base, and the plurality of heaters disposed onthe cantilevered beam; and actuating a light source to generate lightthat is coupled to an optical waveguide that is positioned on the baseand the cantilevered beam and extends from the base along thecantilevered beam.
 16. The system of claim 15, wherein the cantileveredbeam includes a proximal end attached to the base and a distal end, andwherein actuating the plurality of heaters induces oscillation of thedistal end of the cantilevered beam.
 17. The system of claim 15, whereinthe optical scanning device includes one or more capacitive sensingelectrodes disposed on the cantilevered beam or adjacent to thecantilevered beam.
 18. The system of claim 17, wherein the operationsfurther comprise: detecting a capacitance signal corresponding to acapacitance between the capacitive sensing electrodes, wherein thecapacitance is representative of a position of the cantilevered beam.19. The system of claim 15, wherein the light source is a laser diode,and wherein the light is a laser light.